Figure 1
Attachment behavior in knockout pups (μ-KO) and wild-type (WT) pups. (a) Mean number, duration and frequency modulation (difference between the highest and the lowest peak frequency within each element) of ultrasounds emitted by 8-day old pups during 5 min of isolation in a clean or home-cage bedding beaker. WT pups exposed to clean bedding significantly differed from μ-KO pups isolated in clean bedding and from WT pups tested in their mother/best bedding. Sample sizes: μ-KO pups in clean bedding: N=18, in home-cage bedding: N=15; WT pups in clean bedding: N=18, in home-cage bedding: N=15. (b) Percentage of entries (100 × entries mother’s compartment/(entries mother’s compartment + entries unknown mother–litter compartment) and time (100 × time mother’s compartment/(time mother’s compartment + time unknown mother–litter compartment) spent by 10-day old pups in the compartment scented by their mother/nest bedding versus a compartment containing bedding from an unknown mother with its litter. WT pups significantly preferred their mother/nest compartment, whereas μ-KO pups did not. Sample sizes: μ-KO male pups: N=15, female pups: N=13; WT male pups: N=18, female pups: N=22. *P<0.05.
